Multiple indicating telltales having sequential indications

ABSTRACT

Apparatus for providing information as to a plurality of conditions using a single air core gauge. Each condition being monitored controls a switch that in turn controls the energization of at least one winding, the magnetic fields generated by the windings forming a resultant magnetic field that controls the orientation of an indicia-bearing rotatable disc. When one or more windings are energized a lamp illuminates the indicia which the disc locates at a certain position so as to indicate the status of the condition which caused energization of the winding. A provision is also made to index the disc between a plurality of positions so as to advise of several conditions which may require attention at the same time.

United States Patent Fales 51 June 20, 1972 3,375,512 3/1968 Watkins ..340/373 Primary E.\'aminer-Harold l. Pitts [72] Inventor: Douglas 1. Fales, Flint, Mich- Att0rneyJ. L. Carpenter and Paul Fitzpatrick 73 Ass nee: General Motors Co ration, Detroit, 1 1g Mich. rpo [57] ABSTRACT [22] Filed: Nov. 20, 1970 Apparatus for providing information as to a plurality of conditions using a single air core gauge. Each condition being moni- PP 91,393 tored controls a switch that in turn controls the energization of at least one winding, the magnetic fields generated by the [52] U s 340/373 340/378 windings forming a resultant magnetic field that controls the l 5 I] 5/24 d 5/30 orientation of an indicia-bearing rotatable disc. When one or more windings are energized a lamp illuminates the indicia [58] Field of Search ..340/378, 373 which the disc locates at a certain position so as m indicate the status of the condition which caused energization of the wind- [56] References cued ing. A provision is also made to index the disc between a plu- UNITED STATES PATENTS rality of positions so as to advise of several conditions which may require attention at the same time. 3,113,301 12/1963 Templin ..340/378 3,166,744 1/1965 Leonchick 4 Claims, 6 Drawing Figures 9F 5; RING 1 97 cou NT E R g a 5? 98 45 OR a :8

8 78 AND 70 a .F e

E #7 L AND Z1 60 I9 a 49 AND AND 5 72 7. 83

217 NAN D AN D M 46 57 82 52 OR ND PATENTEDJUH 20 I972 SHEET 10F 2 ATTORNEY PliTENTEnJunzo 1972 OSC.

SHEET 2 BF 2 RING COUNTER AND RING OUNTER AND NAND AND E 48 y fi OR AND /85 1 AND INVENTOR 6 By Douglas [fillers 742M? zz TTORNEY and, more particularly, to motor vehicle systems for monitoring a plurality of conditions at various remote locations in a motor vehicle and for indicating the status of the conditions being monitored. This invention also relates to my copending applications which were filed this day and share common ownership with the subject invention. These copending applications were filed on Nov. 20, 1970 and are identified by their U.S. Ser. No. 91,490 and 91,491, respectively.

Many warning systems for advising of conditions in a motor vehicle are presently in widespread use. These systems may, for example, be employed to monitor fuel level in a gas tank, coolant level in a radiator, oil pressure in an engine crankcase, or the charging of a battery by an electrical generating system. Generally, these prior systems are of two types: they either provide a continuous indication of the condition being monitored, the well-known fuel gauge being one example, or they advise the vehicle occupant only of a condition which has changed to such an extent as to need his attention, as is the case with lamps which are employed as telltales. In either event these systems have had to compete for space with many other devices which must also be located in a vehicle dashboard so as to be within reach and observation of the vehicle operator. Since the motoring public is provided an opportunity to enjoy an ever-increasing number of comfort and convenience features offered by vehicle manufactures, the space limitations in vehicle dashboards are continuously becoming more acute.

Accordingly, it is an object of this invention to provide apparatus which monitors a large number of conditions in a motor vehicle and which employs a single dashboard unit to convey information regarding the various monitored conditions to the vehicle operator.

A further object of this invention is the implementation of a single air core gauge to monitor a plurality of conditions at various locations in a motor vehicle. I

Another object of this invention is the provision of an air core gauge which indicates a plurality of conditions in a motor vehicle and which only provides an aifirmative indication as to the status of the monitored conditions which the attention of the vehicle operator to one or more of the conditions is required.

It is another object of this invention to provide apparatus which monitors several conditions in a motor vehicle and which simultaneously advises a vehicle occupant that two or more conditions require his attention by alternately indicating the status of the monitored conditions which require his attentron.

It is yet a further object of this invention to provide an indicator which monitors several conditions in a motor vehicle and advises the vehicle occupant as to the status of the conditions, a continuous indication of malfunctioning conditions being provided when a single condition needs his attention and alternating indications being provided the vehicle operator when more than one monitored condition requires his attention.

The satisfaction of the foregoing objects and the advantages of the subject invention will be apparent from the accompanying description and drawings, in which:

FIG. 1 depicts an air core gauge of the prior art which may be employed in practicing the subject invention.

FIG. 2 is a perspective view, with parts broken away, of an indicator embodying the principles of the subject invention.

FIG. 3 is a cross-sectional view of the indicator in FIG. 1.

FIG. 4 is a schematic representation of an indicator circuit according to the principles of the subject invention.

FIG. 5 is a modification of the indicator circuit in FIG. 4 having provision for alternately advising a vehicle operator of a plurality of conditions.

FIG. 6 is a modification of the indicator circuit in FIG. 5 having a provision for continuously indicating the status of a single condition and forintermittently advising as to the status of a plurality of conditions.

Referring now to the drawings, FIG. I shows an air core gauge 10 of the type disclosed in Ziegler, US. Pat. No. 3,302,191, which may be employed in practicing the subject invention. As shown in FIG. 1, the gauge 10 includes winding support member 12 on which are disposed first and second coils l4 and 16. 'I'I-Ie first coil 14 includes a first set of coaxial windings l8 and 20 and the second coil includes a second set each other, which causes the magnetic fields produced by the windings 18 through 21 to combine in a resultant magnetic field in which the magnetic fields of the opposed windings are cancelled when the opposed windings are equally energized. In addition, the gauge 10 also includes a permanent magnet armature 22 rotatably supported by a shaft 24 that is restrained in a guideway 26.

As shown in FIGS. 2 and 3, an indicator 28 according to the preferred and illustrated embodiment includes the gauge 10 of FIG. 1 disposed with the shaft 24 vertical and drivably connected to a rotatable disc 30, which has a depending edge 32 so as to rotate the disc 30 in accordance with the energization of the windings 18 through 21. A plurality of windows 34 through 37 which bear indicia are disposed inthe depending edge 32 of the disc 30 so as to be aligned with a light source, such as a lamp 38, that is mounted in a shroud behind the depending edge 32 of the disc 30. The lamp 38 and the winding support member 12 are held in a fixed relative position by suitable supporting apparatus, such as a bracket 42 illustrated in FIG. 3.

Accordingly, as a condition which is being monitored effects a change in the energization of the windings 18 through 21 the corresponding change in the resultant magnetic field causes the armature 22 to rotate to a new position in which 0 one of the windows 34 through 37 and the indicia which it bearsv is aligned with the lamp '38. Upon energization of the lamp 38 the window is illuminated by the lamp'38 and the vehicle occupant is made aware of the change inthe condition being monitored.

For example, if it is assumed that the lamp 38 and the windings 18 through 21 are all normally deenergized and that one of the windings 18 through 21 is responsive to the temperature of the vehicle engine, the lamp 38 is normally deenergized and the vehicle operator is therefore not affirmatively advised of any malfunction of the conditions being monitored in the vehicle. That is, so long as the lamp 38 remains deenergized he may assume that the conditions being monitored are functioning normally. However, should the engine temperature exceed a predetermined level the winding with which it is associated will be immediately energized and at a predetennined time after the winding is energized the lamp 38 will be energized, as will subsequently be explained. Accordingly, the disc 30 is first rotated so as to align the window 36, on which is the indicia HOT, with the lamp 38 and then the lamp 38 is energized. Upon energization of the lamp 38 the vehicle operator is advised of the overheated condition of the engine.

A control circuit 44 for controlling the energization of the windings 18 through 21 and the lamp 38 is schematically illustrated in FIG. 4. As shown in FIG. 4, several detection networks 46 through 49 are provided for monitoring various conditions in a vehicle. Each detection network 46 through 49 includes one of a plurality of normally open switches 50 through 53 connected in series with one of the respective windings 18 through 21. Power is supplied to the windings 18 through 21 by a suitable power source, such as a vehicle battery 54, through a power switch, such as a vehicle ignition switch 56, in accordance with the setting of the switches 50 through 53. A resistor 58 is connected in series with the windings 18 through 21 and the battery 54 so as to form a voltage divider in which the common junction 60 of the windings 18 through 21 undergoes a wide voltage excursion in accordance with the energization of the windings 18 through 21, the voltage excursion being sensed by a PNP transistor 62 which controls the energization of the lamp 38.

So long as all the switches 50 through 53 are open substantially the entire voltage of the battery 54 is applied through the ignition switch 56 and the resistor 58 to the common junction 60 of the windings 18 through 21. Accordingly, the base 64 of the transistor 62, which is connected to the junction 60, is at substantially the same voltage as the emitter -66 of the transistor 62 so the transistor 62 is biased to its nonconductive condition. The transistor 62 thus normally prevents energization of the lamp 38, which is in series with the collector 68 of the transistor 62.

However, should one of the switches 50 throughv53, such as the switch 52, be closed due, for example, to an overheated engine, the junction 60 of the windings 18 through 21 would be at a relatively low potential that is established by the voltage divider action of the resistor 58 in series with the winding 20. Since the resistance of the winding 20 is relatively small, the base 64 of the transistor 62 would thus be at a much lower voltage than the emitter 66 and the forward biased baseemitter junction of the transistor 62 makes the transistor 62 conductive so as to energize the lamp 38. Accordingly, the energization of the winding 20 causes the disc 30 to be rotated so as to align the window 36 with the lamp 38 and the energization of the lamp 38 illuminates both the window 36 and the indicia which it contains so as to advise the vehicle operator that the overheated engine needs his attention.

- It should be noted that the time constant formed by the resistor 58 and one of the windings 18 through 21 when the corresponding switch of the switches 50 through 53 is closed pro vides a valuable time delay in the operation of the indicator 28. Since the disc 30 in all probability is not aligned with the lamp 38 for a proper indication the moment one of the switches 50 through 53 is closed, the disc 30 begins to rotate assoon as one of the windings 18 through 21 is energized. ,If the lamp 38 also were immediately energized when one of the windings 18. through 21 becomes energized the indicator 28 may give an initial indication that is erroneous due to the motion of the disc 30. Accordingly, the windings 18 through 21 and the resistor 58 are selected so that the voltage at the junction 60 is decreased at a sufficiently slow rate when one of the switches 50 through 53 is closed as to introduce a certain time delay into the control circuit 44.

By properly selecting the windings 18 through 21 and the resistor 58, the junction 60 voltage is maintained at a sufiiciently high voltage as to maintain the transistor 62 nonconductive until an energized winding has aligned the disc 30 for a proper indication of the malfunction. The disc 30 is thus always properly aligned before the lamp 38 is energized. As persons versed in the art will appreciate, various other time delay circuitry could also be employed to further delay the energization of the lamp 38 after closure of one of the switches 50 through 53. Indeed, the lamp 38 may be selected to be of a type in which the lamp is not illuminated for a certain time after the lamp is energized. A slow lamp, as these lamps are sometimes called, would preclude false indications by the indicator 28 before the disc 30 is properly aligned and would therefore eliminate the need for additional time delay apparatus. I

The control circuit 44 in the embodiment illustrated in FIG. can simultaneously indicate more than one malfunction. This-embodiment difi'ers from that in FIG. 4 by the addition of transistors 70 through 73 in series with each of the respective detection networks 46 through 49. The collectors of the transistors 70 through 73 are connected together at the junction 60 and the bases of the transistor 70 through 73 are each connected to different stages of a ring counter 74 that is driven by anoscillator 76. The transistors 70 through'73 are of an PNP type and are connected to the detection networks 46 through 49 so as to allow current through the windings 18 through 21 only when the emitter of the corresponding transistor is at a relatively low voltage while the base of the transistor is at a relatively high voltage, which would forward bias the base-emitter junction of the transistor and allow it to become conductive. Since the common collectors of the transistors through'73 are normally at a high voltage by virtue of the junction 60 being connected to the battery 54 through the resistor 58 and the ignition switch 56, the ring counter 74 is selected to be of a type which provides grounds to all but one of the bases of the transistors 70 through 73, a very high potential being applied by the ring counter 74 to the base of the other transistor. Of course, as is customary with ring counters, the high voltage output provided by the ring counter 74 is sequentially applied to all of the baes of the transistors 70 through 73 at a rate determined in accordance with the oscillator 76 output.

When in operation, the control circuit 44 of FIG. 5 normally allows a high voltage from the battery 54 to be applied through the ignition switch 56 and the resistor 58 to the common collectors of the transistors 70 through 73. During this time the ring counter 74 is sequentially applying a high voltage to the bases of the transistors 70 through 73. However, the transistors 70 through 73 cannot become conductive so long as the switches 50 through 53 are open. Accordingly, the windings 18 through 21 normally remain deenergized. In the event one of the switches 50 through 53 is closed, however, the transistor in series with the closed switch will thereafter become conductive whenever a high voltage is applied to its base by the ring counter 74.

For example, should the switch 52 be closed by the oil pressure in the vehicle engine falling below. a certain level the transistor 72 will thereafter become conductive and the winding 20 will be energized whenever a high voltage is applied to the base of the transistor 72 by the ring counter 74, which switches the transistor 72 to a conductive condition. Since the impedance across the transistor 72 is very small when the transistor 72 is conductive and the winding 20 is selected to have a relatively low impedance, the common junction 60 of the collectors will thus be at a relatively low potential when the transistor 72 is conductive and at a high potential when none of the transistors 70 through 73 are conductive. The junction 60 thus undergoes wide voltage excursions when one of the transistors 70 through 73 is conductive and these voltage excursions cause the transistor 62 to become conductive and the'lamp 38 to become energized in the fashion previously described.

The energization of the lamp 38 during the course of these voltage excursions is assured by selecting the oscillator 76 to generate signals of a period longer than the time delay required for the transistor 62 to become conductive after one of the windings 18 through 21 is energized. The disc 30 is thus rotated and the lamp 38 is energized each time one of the windings 18 through 21 is energized. The vehicle operatoris therefore intermittently provided with an indication as to the malfunction which has occurred in the vehicle. Indeed, since the lamp 38 is intermittently energized the resultant flashing of the lamp 38 may in some instances more rapidly call the attention of the vehicle operator to the existence of the malfunction than may be the case if the lamp 38 were continuously energized.

Should more than one of the switches 52 through 53 in the control circuit 44 of FIG. 5 be closed by simultaneously occurring malfunctions in the vehicle the ring counter 74 will alternately cause the indication of one and then the other of the malfunctions in the fashion just described. For example, if both of the switches 51 and 52 are closed by malfunctions in the vehicle the indicator 28 will indicate one malfunction when the ring counter 74 applies a high voltage to the base of the transistor 71 and will indicate the other malfunction when the ring counter 74 applies a high voltage to the base of the transistor 72. By making the period of the oscillator 76 sufficiently long, such as 1 second, there is ample opportunity for the disc 30 to be rotated into the proper position for indicating each of the malfunctions.

Due to the sequential nature of the ring counter 74 it is possible in the control circuit 44 of FIG. 5 that there will be a disproportionate time delay between indications of two malfunctions due to the energization of two adjacent coils, as in the example just recited. This disproportionate time delay would occur while the ring counter 74 sequentially applies a high voltage to the gates of the transistors 73 and 70 between indications of the just discussed malfunctions. However, since the indicator 28 may be made to operate relatively slowly by merely increasing the period of the oscillator 76 an ample opportunity is provided the vehicle operator to be advised of all the malfunctions in the vehicle regardless of the order in which the windings 18 through 21 are energized.

In the embodiment of FIG. 6, the control circuit 44 of FIG. 5 has been modified to provide for continuous energization of a winding when the switch in series with the winding is closed by a malfunction. In the event two or more of the switches 50 through 53 are closed at the same time the operation of the control circuit 44 in FIG. 6 reverts to that disclosed in connection with FIG. 5, that is, each of the malfunctions is intermittently indicated to the vehicle operator.

In the embodiment illustrated in FIG. 6 the switches 50 through 53 are each connected to a first OR gate 78. Since the first OR gate 78 only produces an output signal when it is provided one or more input signals, the input signal in this embodiment being a connection to ground through one of the switches 50 through 53, the first OR gate 78 output indicates whether a malfunction has occurred in one of the conditions being monitored by the indicator 28.

In addition, in the FIG. 6 embodiment two of the switches 50 through 53 are connected to each of several AND gates 80 through 85 and the outputs of the AND gates 80 through 85 are connected to a second OR gate 86. Since an AND gate cannot produce an output signal unless an input signal is applied to each of its inputs, the input signal again being a connection to ground through one of the switches 50 through 53, none of the AND gates 80 through 85 produce an output signal unless two or more of the switches 50 through 53'are closed. Accordingly, since the AND gates 80 through 85 are supplied with every combination of two signals which the switches 50 through 53 can produce, whenever two or more of the switches 50 through 53 are closed at least one of the AND gates 80 through 85 will supply a signal to the second OR gate 86. The second OR gate 86 thus produces an output signal whenever two or more of the switches 50 through 53 are closed, and hence may be used to indicate whether two or more of the switches 50 through 53 are closed.

To provide a single control signal which indicates whether only one of the switches 50 through 53 is closed or whether more than one of the switches 50 through 53 are closed the output signals of the first and second OR gates 78 and 86 are supplied to an AND gate 88, the output signal from the second OR gate 86 first being inverted by a NAND gate 90. Accordingly, the AND gate 88 generates an output signal only when the first OR gate.78 generates an output signal and the second OR gate 86 does not generate an output signal, which is only true when only one of the switches 50 through 53 are closed.

Since the control circuit 44 in FIG. 6 is designed to continuously indicate the presence of a single malfunction in one of the conditions being monitored the AND gate 88 output signal, which contains the information, is connected to the base of an NPN transistor 92 which controls energization of the windings 18 through 21.

The transistor 92 collector is connected to the battery 54 through the ignition switch 56 and the emitter of the transistor 92 is connected through a diode 94 and several resistors 95 through 96 to the respective bases of the transistors 70 through 73. Accordingly, when the AND gate 88 generates an output signal it places the transistor 92 base at a high voltage so as to forward bias the base-emitter junction of the transistor 92, which then applies substantially the entire voltage of the battery 54 through the diode 94 and the resistors 95 through 98 to the respective bases of the transistors 70 through 73. Since a high voltage is applied to both the bases and the collectors of the transistors 70 through 73 closure of one of the transistors 70 through 73 will become conductive when their respective emitters are grounded, which takes place when the switches 50 through 53 are closed. Accordingly, when a malfunction causes one of the switches 50 through 53 to be closed, the transistor in series with the closed switch becomes conductive so as to energize the winding in series with the closed switch, causing the lamp 38 to be energized as previously described.

To assure that the ring counter 74 is unable to render any of the transistors 70 through 73 conductive when the transistor 92 is made conductive by the AND gate 88, the oscillator 76 in FIG. 6 is controlled by the output of the second OR gate 86, to which it is connected by a lead 99. Since the second OR gate 86 only produces an output signal when two or more of the switches 50 through 53 are closed it never can produce an output signal when the transistor 92 is conductive, which occurs when only one of the switches 50 through 53 is closed. Accordingly, by preventing the oscillator 76 from operating unless the second OR gate 86 is generating an output signal the ring counter 74 is prevented from applying a voltage to the bases of the transistors 70 through 73 until at least two of the switches 50 through 53 are closed at the same time, as will now be explained.

When there are no malfunctions among the conditions being monitored all of the switches 50 through 53 remain open. The outputs of the AND gates 80 through and the OR gates 78 and 86 are thus at ground potential or, to use binary nornenclature, are each a zero, or 0, bit. Since the input to the NAND gate 90 is a 0 bit its output is a one, or 1, bit which may, for example, be a DC voltage of a unit magnitude substantially the same as that supplied by the battery 54. With the input to the AND gate 88 being 1 and 0 bits, respectively, the output of the AND gate 88 is a 0 bit that grounds the base of the transistor 92, thus reverse biasing the base-emitterjunction of the transistor 92 so as to keep it turned off. Similarly, the 0 bit output of the second OR gate 86 that is applied to the oscillator 76 keeps the oscillator 76, and hence the ring counter 74, turned off. Accordingly, power consumption of the control circuit 44 in FIG. 6 is kept to a minimum when the switches 50 through 53 are open.

Upon closure of one of the switches 50 through 53, such as the switch 52, due to the occurrence of a'malfunction one of the inputs to the AND gate 85 and an input to the OR gate 78 are grounded through the switch 52. The output of the AND gate 85.remains a 0 bit due to its other input, which is connected to the switch 51, not being grounded. However, closure of the switch 52 changes the output of the OR gate 78 from a 0 bit to a 1 bit. Since a I bit is then applied to each of the AND gate 88 inputs the AND gate 88 output is changed from a 0 bit to a 1 bit so as to forward bias the base-emitter junction of the transistor 92. The transistor 92 is thus made conductive and applies a large voltage through the resistors 95 through 98 to the bases of the transistors 70 through 73. Since the emitter of the transistor 72 is grounded through the switch 52 the base-emitter junction of the transistor 72 is forward biased, turning on the transistor 72.

When the transistor 72 is turned on the current which it conducts energizes the winding 20 and, after the brief time delay caused by the time constant of the resistor 58 and the inductance of the winding 20, the voltage at the junction 60 is sufficiently low to turn on the transistor 62 and cause energization of the lamp 38. Since the oscillator 76 and the ring counter 74 remain disabled by the 0 bit output of the second OR gate 86 the indicator 28 thus provides a continuous indication of the condition which caused closure of the switch 52.

If another of the switches 50 through 53, such as the switch 51, is closed while the switch 52 is closed both of the inputs to the AND gate 85 are grounded so the AND gate 85 output changes from a bit to a I bit, causing the second OR gate 86 to change its output from a 0 bit to a 1 bit. When the output of the second OR gate 86 becomes a 1 bit the oscillator 76 begins to oscillate and the ring counter 74 sequentially applies a high voltage to the bases of the transistors 70 through 73.

In addition, when the second OR gate 86 output becomes a 1 bit the output of the NAND gate 90 is switched to a 0 bit since the NAND gate 90 acts as an inverter. The NAND gate 90 thus applies a 0 bit to the AND gate 88 so as to change the AND gate 88 output to a 0 bit and turn off the transistor 92 by grounding its base. The ring counter 76 is thus the only source of currentfor the bases of the transistors 70 through 73 when the switches 50 through 53 are closed. Accordingly, the ring counter 76 in this example sequentially causes the energization of the windings 19 and 240 as described in regard to FIG.

5, the transistor 92 being protected from the high voltage pulses which the ring counter 74 generates by the diode 94.

lt is thus apparent that the apparatus herein described monitors a large number of conditions by using a single air core gauge and is able to continuously indicate a single malfunction or intermittently indicate several malfunctions among the monitored conditions, through persons versed in the art will appreciate that many modifications of this apparatus in addition to those herein described may be made without departing from the spirit of this invention.

What is claimed is: I

1. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two detection networks each including a winding and switch means responsive to a condition being monitored for controlling energization of the winding, the switch means having a first operative condition in which the winding is prevented from being energized and a second operative condition in which the winding is permitted to become energized, the energized windings generating magnetic fields oriented along their respective axes, which are positioned at-predetermined angles to each other, a controlled switch that may be bimed to conductive and nonconductive states in series with each of the detection networks for controlling the energization of the windings,,means for connecting the controlled switches and the detection networks in series with a power source effective to energize the winding in a certain detection network when the switch means in the certain detection network is in the second operative condition and the controlled switch in series with the certain detection network is in the conductive state, means for sequentially and cyclically biasing each of the controlled switches to its conductivestate and the other controlled switches to their nonconductive state whereby only the winding in the detection network which is'series connected with a controlled switch in its conductive state can become energized, and means for indicating the orientation of the magnetic field when a winding is energized so as to provide an indication as to which of the conditions being monitored has changed sufficiently to effect placement of the switch means responsive thereto in the second operative condition.

2. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two detection networks each including a winding and a switch having conductive and nonconductive states responsive to one of the conditions being minitored, the switch and the winding in each detection network being series connected whereby the winding may become energized when the switch in series therewith is placed in the conductive state by the condition which it monitors and is precluded from becoming energized when the switch in series therewith is in the nonconductive state, the energized windings generating magnetic fields oriented along their respective axes, which are located at predetermined an gles to each other, a transistor series connected with each of the detection networks, each transistor having a control terminal towhich a first biaspotential may be applied so as to place the transistor in a nonconductive state and to which a second bias potential may be applied so as to place the transistor in a conductive state, means for connecting the detection networks and the transistors in series with a power source effective to energize one of the windings when both the switch and the transistor in series with the winding are in a conductive state, each of the windings remaining deenergized so long as either the switch or the transistor in series therewith is in a nonconductive state, means for applying the first bias and means for indicating the orientation of the magnetic field when one of the windings is energized so as to provide an indication as to which of the conditions being monitored has caused placement of the switch responsive thereto in the conductive state.

3. Apparatus for indicating the status of a plurality of condi- I tions comprising, in combination, at least two detection networks each including a winding in series with a switch that is responsive to one of the conditions being monitored, each of the switches being open until a change in the condition being monitored effects closure of the switch responsive thereto, a transistor having conductive and nonconductive conditions in series with each of the detection networks, each transistor being nonconductive until biased to its conductive condition, means for connecting the transistors and the detection networks in series with a power source effective to energize each of thewindings when the transistor in series therewith is biased so as to be conductive while the switch in series therewith is closed, first biasing means responsive to the switches effective to bias all of the transistors to their conductive conditions when only one of the switches is closed so as to effect continuous energization of the winding in series with said closed switch, second biasing means responsive to the switches for sequentially and cyclically biasing each of the transistors to its conductive condition while the remaining transistors are maintained nonconductive when more than one of the switches are closed so as to cyclically and sequentially energize the windings in series with the closed switches, and

means responsive to the windings for indicating whichof the windings is energized so as to provide an indication as to the conditions being monitored which changed sufficiently to close the respective switches.

4. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two normally open switches responsive to respective conditions being monitored the switches being closed by a change in the respective conditions being monitored, a winding connected in series circuit with each of the switches, the windings being disposed with their axes at predetermined angles to each other whereby the windings when energized generate magnetic fields oriented along their respective axes, a transistor connected in each of the series circuits, means for connecting the series circuits to a power source so that each of the transistors is effective to prevent energization of the winding in series therewith unless the switch that is also in series therewith is closed and the transistor is biased to a conductive condition, first biasing means responsive to the switches for biasing all of the transistors to the conductive condition when only one of the switches is closed so as to effect continuous energization of the winding in series with the closed switch, second biasing means responsive to the switches for sequentially and cyclically biasing each of the transistors to the conductive condition while the remaining transistors are maintained noncon-' ductive when more than one of the switches are closed so as to cyclically and sequentially energize the windings in series with the closedswitches, the second biasing means including a ring counter that cyclically and sequentially applies a bias potential to each of the transistors while the remaining transistors are maintained nonconductive for cyclically and sequentially biasing the transistors to their conductive condition and an oscilla- 

1. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two detection networks each including a winding and switch means responsive to a condition being monitored for controlling energization of the winding, the switch means having a first operative condition in which the winding is prevented from being energized and a second operative condition in which the winding is permitted to become energized, the energized windings generating magnetic fields oriented along their respective axes, which are positioned at predetermined angles to each other, a controlled switch that may be biased to conductive and nonconductive states in series with each of the detection networks for controlling the energization of the windings, means for connecting the controlled switches and the detection networks in series with a power source effective to energize the winding in a certain detection network when the switch means in the certain detection network is in the second operative condition and the controlled switch in series with the certain detection network is in the conductive state, means for sequentially and cyclically biasing each of the controlled switches to its conductive state and the other controlled switches to their nonconductive state whereby only the winding in the detection network which is series connected with a controlled switch in its conductive state can become energized, and means for indicating the orientation of the magnetic field when a winding is energized so as to provide an indication as to which of the conditions being monitored has changed sufficiently to effect placement of the switch means responsive thereto in the second operative condition.
 2. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two detection networks each including a winding and a switch having conductive and nonconductive states responsive to one of the conditions being minitored, the switch and the winding in each detection network being series connected whereby the winding may become energized when the switch in series therewith is placed in the conductive state by the condition which it monitors and is precluded from becoming energized when the switch in series therewith is in the nonconductive state, the energized windings generating magnetic fields oriented along their respective axes, which are located at predetermined angles to each other, a transistor series connected with each of the detection networks, each transistor having a control terminal to which a first bias potential may be applied so as to place the transistor in a nonconductive state and to which a second bias potential may be applied so as to place the transistor in a conductive state, means for connecting the detection networks and the transistors in series with a power source effective to energize one of the windings when both the switch and the transistor in series with the winding are in a conductive state, each of the windings remaining deenergized so long as either the switch or the transistor in series therewith is in a nonconductive state, means for applying the first bias potential to the control terminal of each transistor so as to place the transistors in the nonconductive state, means for sequentially and cyclically applying the second bias potential to each of the control terminals while the remaining control terminals have the first bias potential applied thereto, thereby sEquentially and cyclically energizing each of the windings which are in series with a switch that is in a conductive state, and means for indicating the orientation of the magnetic field when one of the windings is energized so as to provide an indication as to which of the conditions being monitored has caused placement of the switch responsive thereto in the conductive state.
 3. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two detection networks each including a winding in series with a switch that is responsive to one of the conditions being monitored, each of the switches being open until a change in the condition being monitored effects closure of the switch responsive thereto, a transistor having conductive and nonconductive conditions in series with each of the detection networks, each transistor being nonconductive until biased to its conductive condition, means for connecting the transistors and the detection networks in series with a power source effective to energize each of the windings when the transistor in series therewith is biased so as to be conductive while the switch in series therewith is closed, first biasing means responsive to the switches effective to bias all of the transistors to their conductive conditions when only one of the switches is closed so as to effect continuous energization of the winding in series with said closed switch, second biasing means responsive to the switches for sequentially and cyclically biasing each of the transistors to its conductive condition while the remaining transistors are maintained nonconductive when more than one of the switches are closed so as to cyclically and sequentially energize the windings in series with the closed switches, and means responsive to the windings for indicating which of the windings is energized so as to provide an indication as to the conditions being monitored which changed sufficiently to close the respective switches.
 4. Apparatus for indicating the status of a plurality of conditions comprising, in combination, at least two normally open switches responsive to respective conditions being monitored the switches being closed by a change in the respective conditions being monitored, a winding connected in series circuit with each of the switches, the windings being disposed with their axes at predetermined angles to each other whereby the windings when energized generate magnetic fields oriented along their respective axes, a transistor connected in each of the series circuits, means for connecting the series circuits to a power source so that each of the transistors is effective to prevent energization of the winding in series therewith unless the switch that is also in series therewith is closed and the transistor is biased to a conductive condition, first biasing means responsive to the switches for biasing all of the transistors to the conductive condition when only one of the switches is closed so as to effect continuous energization of the winding in series with the closed switch, second biasing means responsive to the switches for sequentially and cyclically biasing each of the transistors to the conductive condition while the remaining transistors are maintained nonconductive when more than one of the switches are closed so as to cyclically and sequentially energize the windings in series with the closed switches, the second biasing means including a ring counter that cyclically and sequentially applies a bias potential to each of the transistors while the remaining transistors are maintained nonconductive for cyclically and sequentially biasing the transistors to their conductive condition and an oscillator that is responsive to the switches and effective when two or more of the switches are closed to apply an alternating voltage to the ring counter whereby the ring counter cyclically and sequentially biases the transistors to the conductive condition at a rate determined by the frequency of the alternating voltage, and means responsive to the energization of the windings for indicating the monitored conditions which change sufficiently to close the respective switches. 